Pulse-width-modulated (PWM) controllers are frequently used to control electrical devices such as various types of motors. For example, one type of motor often controlled by a PWM drive system is the brushless direct current (BLDC) motor. In the case of poly-phase BLDC motors, such as a three-phase BLDC motor, the controller/driver is typically configured with half-bridge assemblies connected to respective phase windings of the BLDC motor.
The speed of a BLDC motor is generally controlled by a PWM driver, where the average currents in the phase windings are typically generated by the “on” and “off” states of the PWM input voltage signals. That is, the duty cycle of the input voltage pulse signals can be used as a controlling factor for the average current in the phase windings, in order to determine the speed of the motor.
The upper speed capability of a conventional PWM motor driver is typically limited to the maximum frequency capability of the switching elements in the half-bridge circuits used to drive the phase windings of the motor. For example, a standard driver with insulated gate bipolar transistor (IGBT) switching elements can typically drive a three-phase motor with a maximum switching frequency of approximately 20 kHz, assuming the maximum IGBT current is not required for more than a few minutes. As such, conventional motor drivers using IGBT switching elements are generally limited to frequency applications up to 20 kHz. While other types of devices commonly used as switching elements, such as the field effect transistor (FET), are capable of operating at higher frequencies, the power capability of a FET is generally limited by its maximum voltage range of approximately 200 volts. Other types of switching devices with higher frequency and power capabilities may be available, but their cost is typically many times higher than the cost of a standard component, such as an IGBT. As such, the costly high frequency, high power devices are generally considered undesirable for production applications.
Current trends in motor design include ever increasing requirements for combinations of high power and high frequency driver capabilities. For example, one recent application specified a motor controller capable of operating at a frequency of approximately 125 kHz, and at a power level requiring IGBT capability. Therefore, there is a need for a frequency scalable type of driver to operate at relatively high frequencies, and over a range of power levels. Moreover, this type of scalable driver could be suitable for production applications if it were configured with standard low-cost components.
Accordingly, it is desirable to provide a controller/driver for BLDC and other motor applications with scalable frequency capabilities over a range of power levels. In addition, it is desirable to implement the scalable driver with low-cost components for production applications. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.